The subject matter disclosed herein relates to a welding system. Specifically, the subject matter disclosed herein relates to a welding system configured to weld a sealed component (e.g., a pressure vessel, turbine rotor forgings, etc.) having purge holes along a weld seam.
Conventional welding systems used for welding a sealed component include a dual-torch system, where the torches are located opposite one another on a common axis. The sealed component includes purge holes displaced along the weld seam of the sealed component. As the sealed component rotates and the torches begin to weld the component, the unwelded purge holes aid in minimizing pressure difference between the sealed cavity and the exterior. Just prior to the final purge hole being welded by the torches, heat from the torches causes the temperature to rise within the cavity of the sealed component, and thereby increase the pressure within the cavity. This increase in pressure within the cavity can cause unacceptable weld morphology, or even weld rupture of the root (i.e., weld root blow out, weld root fall in, etc.) as the final purge hole is welded and the cavity is sealed.
In order to avoid unacceptable weld morphology or weld rupture of the sealed component, a bore or permanent pressure release hole is sometimes incorporated into the sealed component. However, the use of a permanent pressure release hole creates new problems for the sealed component, including a high stress state surrounding the permanent pressure release hole while the component is being utilized within a system (i.e., steam-turbine energy system, etc.). A permanent release hole of the sealed component can also serve as a stress concentrator and increase the risk of cracking or mechanical failure, which may require expensive repair and/or complete replacement of the sealed component. Furthermore, the permanent pressure release hole may require continuous inspections, which may be costly and inconvenient to a user.
Use of a single torch welding system may significantly reduce the heat added to the component during welding, and thus reduce the pressure within the cavity while welding the final purge hole. This approach may reduce the likelihood of unacceptable weld concavity, or weld blow-through. However, the single torch welding system increases the amount of time required to complete a proper weld of the sealed component. Additionally, a single torch creates an uneven distribution of heat along the weld seam. This uneven distribution of heat of the weld seam may create angular distortion in the weld, prevent the sealed component from being cylindrically uniform, and, as a result, may cause the sealed component to be unsuitable for use in systems that require strict cylindrical uniformity (i.e., steam-turbine energy system, etc.)